U.S. patent number 6,525,477 [Application Number 09/867,076] was granted by the patent office on 2003-02-25 for optical magnetron generator.
This patent grant is currently assigned to Raytheon Company. Invention is credited to James G. Small.
United States Patent |
6,525,477 |
Small |
February 25, 2003 |
Optical magnetron generator
Abstract
An optical magnetron generator is provided which includes an
anode and a collector separated by an anode-collector space, a pair
of output terminals operatively coupled to the anode and the
collector to provide an electrical power output based on an
electric field generated across the anode-collector space. The
optical magnetron generator further includes one magnet arranged to
provide a dc magnetic field within the anode-collector space
generally normal to the electric field, and a plurality or resonant
cavities each having an opening along a surface of the anode which
defines the anode-collector space; an input for receiving
electromagnetic radiation from an external source and operatively
configured to introduce the optical radiation into the
anode-cathode space to establish a resonance electromagnetic field
within the resonance cavities. A cathode for introducing electrons
into the anode-collector space in proximity to the resonant
electromagnetic filed, wherein the resonant electromagnetic field
accelerates the electrons within the anode-collector space towards
the collector onto which at least one portion of the electrons are
collected.
Inventors: |
Small; James G. (Tucson,
AZ) |
Assignee: |
Raytheon Company (Lexington,
MA)
|
Family
ID: |
25349036 |
Appl.
No.: |
09/867,076 |
Filed: |
May 29, 2001 |
Current U.S.
Class: |
315/39.51;
315/39.77 |
Current CPC
Class: |
H01J
23/213 (20130101); H01J 23/22 (20130101); H01J
25/50 (20130101) |
Current International
Class: |
H01J
25/00 (20060101); H01J 25/50 (20060101); H01J
025/50 () |
Field of
Search: |
;315/39.51,39.53,39.65,39.75,39.77 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Partial International Search Report Re: PCT/US01/16622 mailed on
Nov. 13, 2001 with Invitation to Pay Additional Fees..
|
Primary Examiner: Wong; Don
Assistant Examiner: Tran; Thuy Vinh
Attorney, Agent or Firm: Renner, Otto, Boisselle &
Sklar
Claims
What is claimed is:
1. An optical magnetron generator, comprising: an anode and a
collector separated by an anode-collector space; a pair of output
terminals operatively coupled to the anode and the collector to
provide an electrical power output based on an electric field
generated across the anode-collector space; at least one magnet
arranged to provide a dc magnetic field within the anode-collector
space generally normal to the electric field; a plurality of
resonant cavities each having an opening along a surface of the
anode which defines the anode-collector space; an input for
receiving electromagnetic radiation from an external source and
operatively configured to introduce the optical radiation into the
anode-cathode space to establish a resonant electromagnetic field
within the resonant cavities; and a cathode for introducing
electrons into the anode-collector space in proximity to the
resonant electromagnetic field, wherein the resonant
electromagnetic field accelerates the electrons within the
anode-collector space towards the collector onto which at least a
portion of the electrons are collected.
2. The magnetron generator of claim 1, wherein the resonant
cavities are each designed to resonate at a frequency having a
wavelength .lambda. of approximately 10 microns or less.
3. The magnetron generator of claim 1, wherein the plurality of
resonant cavities comprises a plurality of radial slots of
substantially equal depth formed in the anode.
4. The magnetron generator of claim 1, wherein the plurality of
resonant cavities comprises alternating radial slots of at least
two different depths formed in the anode.
5. The magnetron generator of claim 1, wherein the plurality of
resonant cavities comprises a plurality of radial slots, and at
least some of the plurality of radial slots are coupled to a common
resonator.
6. The magnetron generator of claim 5, wherein the common resonator
comprises at least one common resonant cavity around an outer
circumference of the anode.
7. The magnetron generator of claim 6, wherein the common resonator
comprises a single common resonant cavity and among the plurality
of radial slots formed in the anode only every other one is coupled
to the resonant cavity.
8. The magnetron generator of claim 6, wherein the common resonator
comprises a plurality of common resonant cavities around the outer
circumference of the anode.
9. The magnetron generator of claim 8, wherein among the plurality
of radial slots formed in the anode, odd-numbered slots are coupled
to a first of the plurality of common resonant cavities and
even-numbered slots are coupled to a second of the plurality of
common resonant cavities.
10. The magnetron generator of claim 6, wherein the common resonant
cavity has a curved surface defining an outer wall of the
cavity.
11. The magnetron generator of claim 1, wherein at least one of the
plurality of resonant cavities is coupled to the input to input the
electromagnetic radiation having a wavelength .lambda..
12. The magnetron generator of claim 11, wherein the input
comprises a window transparent to incoming electromagnetic
radiation having the wavelength .lambda..
13. A power transmission system comprising: an optical magnetron
generator according to claim 1; and means for providing the
electromagnetic radiation to the input.
14. An optical magnetron generator, comprising: a cylindrical
collector having a radius rc; an annular-shaped anode having a
radius ra and coaxially aligned with the collector to define an
anode-collector space having a width wa=ra-rc; a pair of output
terminals operatively coupled to the anode and the collector to
provide an electrical power output based on an electric field
generated across the anode-collector space; at least one magnet
arranged to provide a dc magnetic field within the anode-collector
space generally normal to the electric field; a plurality of
resonant cavities each having an opening along a surface of the
anode which defines the anode-collector space; an input for
receiving electromagnetic radiation from an external source and
operatively configured to introduce the optical radiation into the
anode-cathode space to establish a resonant electromagnetic field
within the resonant cavities; and a cathode for introducing
electrons into the anode-collector space in proximity to the
resonant electromagnetic field, wherein the electrons introduced by
the cathode are influenced by the resonant electromagnetic field
and the magnetic field to accelerate along a path through the
anode-collector space which curves towards the collector.
15. The magnetron generator of claim 14, wherein the resonant
cavities are each designed to resonate at a frequency having a
wavelength .lambda., and a circumference 2 .pi. ra of the surface
of the anode is greater than .lambda..
16. The magnetron generator of claim 14, wherein the plurality of
resonant cavities comprises a plurality of radial slots of
substantially equal depth formed in the anode.
17. The magnetron generator of claim 14, wherein the plurality of
resonant cavities comprises alternating radial slots of at least
two different depths formed in the anode.
18. The magnetron generator of claim 14, wherein the plurality of
resonant cavities comprises a plurality of radial slots, and at
least some of the plurality of radial slots are coupled to a common
resonator.
19. The magnetron generator of claim 18, wherein the common
resonator comprises at least one common resonant cavity around an
outer circumference of the anode.
20. The magnetron generator of claim 19, wherein the common
resonator comprises a single common resonant cavity and among the
plurality of radial slots formed in the anode only every other one
is coupled to the resonant cavity.
21. The magnetron generator of claim 19, wherein the common
resonator comprises a plurality of common resonant cavities around
the outer circumference of the anode.
22. The magnetron generator of claim 21, wherein among the
plurality of radial slots formed in the anode, odd-numbered slots
are coupled to a first of the plurality of common resonant cavities
and even-numbered slots are coupled to a second of the plurality of
common resonant cavities.
23. The magnetron generator of claim 19, wherein the common
resonant cavity has a curved surface defining an outer wall of the
cavity.
24. The magnetron generator of claim 14, wherein at least one of
the plurality of resonant cavities is coupled to at least one
output port to output electromagnetic energy having a wavelength
.lambda..
25. The magnetron generator of claim 24, wherein the output port
comprises an output window generally transparent to electromagnetic
energy having the wavelength .lambda..
26. The magnetron generator of claim 14, wherein the plurality of
resonant cavities are configured to induce pi-mode resonance.
Description
TECHNICAL FIELD
The present invention relates generally to electrical generators,
and more particularly to a high efficiency optical magnetron
generator for converting optical radiation to electrical power.
BACKGROUND OF THE INVENTION
An optical magnetron for producing high efficiency, high power
electromagnetic energy at very high frequencies is described in
commonly assigned, U.S. patent application Ser. No. 09/584,887,
filed on Jun. 1, 2000, which is now U.S. Pat. No. 6,373,194, and
U.S. patent application Ser. No. 09/798,623, filed on Mar. 1, 2001.
The present invention relates to the applicant's discovery that the
optical magnetron described in the aforementioned application may
operate in an inverse manner as a generator to convert optical
radiation into electrical energy or power.
SUMMARY OF THE INVENTION
The present invention provides an optical magnetron generator which
converts input optical radiation into electrical power.
Resultantly, the generator permits the transmission of electric
power without wires, for example. The generator can be used in
various applications which may include the elimination of electric
power transmission lines, beaming power to satellites or aircraft
from ground stations, and beaming power from orbiting power
stations to earth receivers thus eliminating the pollution of
earth-based power stations.
According to one particular aspect of the invention, an optical
magnetron generator is provided. The optical magnetron generator
includes an anode and a collector separated by an anode-collector
space; a pair of output terminals operatively coupled to the anode
and the collector to provide an electrical power output based on an
electric field generated across the anode-collector space; at least
one magnet arranged to provide a dc magnetic field within the
anode-collector space generally normal to the electric field; a
plurality of resonance cavities each having an opening along a
surface of the anode which defines the anode-collector space; an
input for receiving electromagnetic radiation from an external
source and operatively configured to introduce the optical
radiation into the anode-cathode space to establish a resonant
electromagnetic field within the resonant cavities; a cathode for
introducing electrons into the anode-collector space in proximity
to the resonant electromagnetic field; and wherein the resonant
electromagnetic field accelerates the electrons within the
anode-collector space towards the collector onto which at least a
portion of the electrons are collected.
According to another aspect of the invention, an optical magnetron
generator is provided which includes a cylindrical collector having
a radius rc; an annular-shaped anode having a radius ra and
coaxially aligned with the collector to define an anode-collector
space having a width wa=ra-rc; a pair of output terminals
operatively coupled to the anode and the collector to provide an
electrical power output based on an electric field generated across
the anode-collector space; at least one magnet arranged to provide
a dc magnetic field within the anode-collector space generally
normal to the electric field; and a plurality of resonant cavities
each having an opening along a surface of the anode which defines
the anode-collector space; an input for receiving electromagnetic
radiation from an external source and operatively configured to
introduce the optical radiation into the anode-cathode space to
establish a resonant electromagnetic field within the resonant
cavities; and a cathode for introducing electrons into the
anode-collector space in proximity to the resonance electromagnetic
field, wherein the electrons introduced by the cathode are
influenced by the resonant electromagnetic field and the magnetic
field to accelerate along a path through the anode-collector space
which curves towards the collector.
To the accomplishment of the foregoing and related ends, the
invention, then, comprises the features hereinafter fully described
and particularly pointed out in the claims. The following
description and the annexed drawings set forth in detail certain
illustrative embodiments of the invention. These embodiments are
indicative, however, of but a few of the various ways in which the
principles of the invention may be employed. Other objects,
advantages and novel features of the invention will become apparent
from the following detailed description of the invention when
considered in conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an environmental view illustrating the use of an optical
magnetron generator in accordance with the present invention as
part of an energy conversion system for converting optical
radiation to electrical energy;
FIG. 2 is a cross-sectional view of an optical magnetron generator
in accordance with one embodiment of the present invention;
FIG. 3 is a cross-sectional top view of the optical magnetron
generator of FIG. 2 taken along line I--I;
FIGS. 4a, 4b and 4c are enlarged cross-sectional views of a portion
of the anode in accordance with the present invention, each anode
including resonant cavities according to one embodiment of the
present invention;
FIG. 5 is a cross-sectional view of an optical magnetron generator
in accordance with another embodiment of the present invention;
FIG. 6 is a cross-sectional view of an optical magnetron generator
in accordance with yet another embodiment of the present
invention;
FIG. 7a is a cross-sectional view of an optical magnetron generator
in accordance with still another embodiment of the present
invention;
FIG. 7b is a cross-sectional top view of the optical magnetron
generator of FIG. 7a;
FIG. 8 is a cross-sectional view of an optical magnetron generator
in accordance with a multi-wavelength embodiment of the present
invention;
FIG. 9 is a cross-sectional view of an optical magnetron generator
according to another embodiment of the present invention;
FIG. 10 is an enlarged perspective view of a portion of the anode
showing the input coupling;
FIGS. 11a, 11b and 11c schematically represent an embodiment of the
present invention designed to operate in the TEM.sub.20 mode;
FIGS. 11d, 11e and 11f schematically represent an embodiment of the
present invention designed to operate in the TEM.sub.10 mode;
FIGS. 12a and 12b represent steps used in forming an anode
structure in accordance with one embodiment of the present
invention;
FIG. 13 represents another method for forming an anode structure in
accordance with the present invention;
FIGS. 14a-14c represent steps used in forming a toroidal optical
resonator in accordance with the present invention;
FIG. 15 is a top view of an anode structure formed in accordance
with a wedge-based embodiment of the present invention;
FIG. 16 is a top view of an exemplary wedge used to form the anode
structure of FIG. 15 in accordance with the present invention;
FIGS. 17 and 18 are side views of even and odd-numbered wedges,
respectively, used to form the anode structure of FIG. 15 in
accordance with the present invention;
FIG. 19 is a schematic cross-sectional view of an H-plane bend
embodiment of an anode structure in accordance with the present
invention;
FIG. 20 is a top view of an exemplary wedge used to form the anode
structure of FIG. 19 in accordance with the present invention;
FIG. 21 is a side view of an even-numbered wedge used to form the
anode structure of FIG. 19 in accordance with the present
invention;
FIGS. 22 and 23 are side views of alternating odd-numbered wedges
used to form the anode structure of FIG. 19 in accordance with the
present invention;
FIG. 24 is a schematic cross-sectional view of another H-plane bend
embodiment of an anode structure in accordance with the present
invention;
FIG. 25 is a top view of an exemplary wedge used to form the anode
structure of FIG. 24 in accordance with the present invention;
FIG. 26 is a side view of an even-numbered wedge used to form the
anode structure of FIG. 24 in accordance with the present
invention;
FIG. 27 is a side view of an odd-numbered wedge used to form the
anode structure of FIG. 24 in accordance with the present
invention;
FIG. 28 is a schematic cross-sectional view of another H-plane bend
embodiment of an anode structure in accordance with the present
invention;
FIG. 29 is a side view of every other odd-numbered wedge used to
form the anode structure of FIG. 28;
FIG. 30 is a schematic cross-sectional view of a dispersion-based
embodiment of an anode structure in accordance with the present
invention;
FIG. 31 is a top view of an exemplary wedge used to form the anode
structure of FIG. 30 in accordance with the present invention;
FIGS. 32 and 33 are side view of even and odd-numbered wedges used
to form the anode structure of FIG. 30 in accordance with the
present invention;
FIG. 34 is a side view of an E-plane bend embodiment of an anode
structure in accordance with the present invention;
FIG. 35 is a top view of a linear E-plane layer used to form the
anode structure of FIG. 34 in accordance with the present
invention;
FIG. 36 is an enlarged view of a portion of the linear E-plane
layer of FIG. 35 in accordance with the present invention;
FIG. 37 is a top view of a curved E-plane layer used to form the
anode structure of FIG. 34 in accordance with the present
invention; and
FIG. 38 is an enlarged view of a portion of the curved E-plane
layer of FIG. 37.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention is now described in detail with reference to
the drawings. Like reference numerals are used to refer to like
elements throughout.
Referring initially to FIG. 1, an optical power transmission system
20 is shown. The optical power transmission system 20 includes an
optical magnetron generator 22. The optical magnetron generator 22
serves to convert optical radiation to electrical energy such that
power may be transmitted optically from point-to-point. Although
the optical magnetron generator 22 is described herein in the
context of its use in an optical power transmission system 20, it
will be appreciated that the optical magnetron generator 22 has
utility in a variety of other applications. The present invention
contemplates any and all such applications.
As is shown in FIG. 1, the optical magnetron generator 22 receives
coherent optical radiation 24 such as light in the infrared,
ultraviolet or visible light region. The optical radiation 24
preferably is coherent radiation which has a wavelength
corresponding to a frequency of 100 Ghz or more, although it will
be appreciated that the frequency of the optical radiation 24 could
be in the microwave region as low as 1 GHz without departing frm
the scope of the invention. In a more particular embodiment, the
optical magnetron generator 22 is designed to receive optical
radiation having a wavelength in the range of about 10 microns to
about 0.5 micron. According to an even more particular embodiment,
the optical magnetron generator 22 receives optical radiation
having a wavelength in the range of about 3.5 microns to about 1.5
microns.
The optical radiation 24 received by the optical magnetron
generator 22 has a wavelength .lambda., referred to herein as the
operating wavelength. The optical radiation 24 is provided to the
optical magnetron generator 22 by a coherent light source 30, such
as the optical magnetron disclosed in the aforementioned U.S.
patent application Ser. Nos. 09/584,887 and 09/798,623.
The power transmission system 20 further includes a power supply 32
for providing a dc operating voltage to the optical magnetron
generator 22. As will be explained in more detail below, the
optical magnetron generator 22 operates on a dc voltage provided to
heat the cathode in order to facilitate the emission of electrons.
Of course, an ac voltage could be used to heat the cathode without
departing from the scope of the invention.
Referring now to FIGS. 2 and 3, a first embodiment of the optical
magnetron 22 is shown. The generator 22 includes a cylindrically
shaped collector 40 having a radius rc. Included at the respective
ends of the collector 40 are endcaps 41. The collector 40 is
enclosed within a hollow-cylindrical shaped anode 42 which is
aligned coaxially with the collector 40. The anode 42 has an inner
radius ra which is greater than rc so as to define an interaction
region or anode-collector space 44 between an outer surface 48 of
the collector 40 and an inner surface 50 of the anode 42.
The generator 22 further includes a cathode 51 designed to
introduce electrons into the anode-collector space 44. In the
exemplary embodiment, the cathode 51 has a birdcage design
including a pair of end rings 51a separated by a plurality of legs
51b designed to emit electrons when heated. The cathode 51 is
arranged coaxially with the anode 42 and the collector 44, with the
end rings 51a having a radius slightly less than the inner radius
ra of the anode 42. Thus, the legs 51b of the cathode 51 are spaced
periodically around and proximate to the inner circumference of the
anode 42.
The cathode 51 includes a pair of terminals 52a and 52b which are
coupled to the power supply 32. During operation, current provided
by the power supply 32 passes through the cathode 51, and
specifically through the legs 51b. The resistance and composition
of the legs 51b is selected such that the current passing
therethrough causes each leg to become heated and emit free
electrons. As a result, the cathode 51 introduces the emitted
electrons into the anode-collector space 44. The cathode 51 may be
made of any suitable material, such as those often used as
filaments. For example, a fine tungsten wire arranged in a birdcage
configuration may serve as the cathode 51.
The anode 42 is electrically connected to a positive (+) terminal
56 of the high voltage output. The collector 40 is electrically
connected to a negative (-) terminal 54 of the high voltage
output.
Continuing to refer to FIGS. 2 and 3, the generator 22 further
includes a pair of magnets 58 and 60 located at the respective ends
of the anode 42. The magnets 58 and 60 are configured to provide a
dc magnetic field B in an axial direction which is normal to an
electric field E which is established throughout the
anode-collector space 44. As is shown in FIG. 3, the magnetic field
B is into the page within the anode-collector space 44. The magnets
58 and 60 in the exemplary embodiment are permanent magnets which
produce a magnetic field B on the order of 2 kilogauss, for
example. Other means for producing a magnetic field may be used
instead (e.g., an electromagnet), as will be appreciated. However,
one or more permanent magnets 58 and 60 are preferred particularly
in the case where it is desirable that the optical magnetron
generator 22 provide some degree of portability, for example.
As will be described in more detail below in connection with FIGS.
4a-4c, for example, the inner surface 50 of the anode 42 includes a
plurality of resonant cavities distributed along the circumference.
In the exemplary embodiment, the resonant cavities are formed by an
even number of equally spaced slots which extend in the axial
direction.
The cavities are designed to resonate at the wavelength of the
incoming optical radiation 24 (operating wavelength), and are
spaced apart in pi-mode fashion as is described more fully below.
The incoming optical radiation 24 is introduced into the
anode-collector space 44 directly or via a common resonator, for
example. The incoming optical radiation 24 in turn excites pi-mode
resonance among the resonant cavities. The electrons which are
emitted from the heated cathode 51 are introduced into the
anode-cathode space 44 and in close proximity to the openings of
the resonant cavities. These electrons are influenced by the
pi-mode resonance created by the optical radiation 24. As a result,
the electrons emitted from the heated cathode 51 are bunched
together in pi-mode fashion and accelerated circumferentially by
the resonance condition established by the incoming radiation 24.
The electrons thus form a rotating electron cloud which rotates in
close proximity to the resonant cavities.
The electrons within the electron cloud are accelerated
circumferentially by the pi-mode resonance established by the
optical radiation 24. As the electrons accelerate, they tend to
curve radially inward as a result of the cross magnetic field B.
The faster moving electrons gain sufficient energy so as to spiral
inward where they are collected at the collector 40. Accordingly, a
negative potential charge builds up on the collector 40 relative to
the anode 42. Consequently, an electric potential E is established
across the anode 42 and the collector 40. This potential can be
provided to a load (not shown) via terminals 54 and 56 connected to
the anode 42 and the collector 40, respectively.
As the load draws current from the generator 22 by way of the
charge built up on the collector 40, additional electrons emitted
by the cathode 51 are accelerated circumferentially by the pi-mode
oscillations provided by the resonant cavities and the incoming
radiation 24. Thus, the generator 22 constantly replenishes any
electrons drawn from the collector 40 by the load.
In another embodiment, the electrons captured by the collector 40
may be used to charge a storage device (e.g., capacitor bank) (not
shown) or the like from which the load ultimately draws the energy.
The present invention encompasses any such variations.
As previously mentioned, the generator 22 includes a relatively
large number of resonant cavities within the anode 42. These
resonant cavities are preferably formed using high precision
techniques such as photolithography, micromachining, electron beam
lithography, reactive ion etching, etc., as will be described more
fully below. The generator 22 has a relatively large anode 42
compared to the operating wavelength .lambda., such that the
circumference of the inner anode surface 50, equal to 2 .pi. ra, is
substantially larger than the operating wavelength .lambda..
In the exemplary embodiment of FIG. 2, every other resonant cavity
includes a coupling port 64 which serves to couple energy from the
respective resonant cavities to a common resonant cavity 66. The
coupling ports 64 are formed by holes or slots provided through the
wall of the anode 42. The resonant cavity 66 is formed around the
outer circumference of the anode 42, and is defined by the outer
surface 68 of the anode 42 and a cavity defining wall 70 formed
within a resonant cavity structure 72. As is shown in FIGS. 2 and
3, the resonant cavity structure 72 forms a cylindrical sleeve
which fits around the anode 42. The resonant cavity 66 is
positioned so as to be aligned with the coupling ports 64 from the
respective resonant cavities. The resonant cavity 66 serves to
constrain the plurality of resonant cavities to operate in the
pi-mode as is discussed more fully below in connection with FIG.
4c.
In addition, the cavity structure 72 may serve to provide
structural support to the anode 42 which in many instances will be
very thin. The cavity structure 72 also facilitates cooling the
anode 42 in the event of high temperature operation.
The common resonant cavity 66 includes at least one or more input
ports 74 which serve to couple coherent optical radiation 24 at the
operating wavelength .lambda. into the resonant cavity 66 via a
corresponding transparent input window 76. The input port(s) 74 are
formed by holes or slots provided through the wall of the resonant
cavity structure 72. The input window(s) 76 preferably are each
formed by a partially transmissive mirror designed to allow the
optical radiation 24 to pass through freely; whereas the radiation
from within the anode-collector space 44 tends to be electrically
reflected by the input window 76.
The structure shown in FIGS. 2 and 3, together with the other
embodiments described herein, is preferably constructed such that
the anode-collector space 44 and resonant cavity 66 are maintained
within a vacuum. This prevents dust or debris from entering into
the device and otherwise disturbing the operation thereof.
FIG. 4a represents a cross-sectional view of a portion of the anode
42 according to a general embodiment. The cross-section is taken in
a plane which is perpendicular to the common axis of the anode 42
and cathode 40 as will be appreciated. The curvature of the anode
42 has not been shown for ease of illustration. As is shown, each
resonant cavity within the anode 42 is represented by a slot 80
formed at the surface 50 of the anode 42. In the exemplary
embodiment, the slots 80 have a depth d equal to .lambda./4 to
allow for resonance, where .lambda. represents the wavelength of
the input optical radiation 24 at the desired operating frequency.
The slots 80 are spaced apart a distance of .lambda./2 or less, and
each slot has a width w equal to .lambda./8 or less. The slot width
w should be .lambda./8 or less to allow electrons to pass the slot
80 before the electric field reverses in pi-mode operation as can
be shown.
The total number N of slots 80 in the anode 42 is selected such
that the electrons moving through the anode-collector space 44
preferably are moving substantially slower than the speed of light
c (e.g., approximately on the order of 0.1 c to 0.3 c). The slots
80 are evenly spaced around the inner circumference of the anode
42, and the total number N is selected so as to be an even number
in order to permit pi-mode operation. The slots 80 have a length
which may be somewhat arbitrary, but preferably is similar in
length to the cathode 40. For ease of description, the N slots 80
may be considered as being numbered in sequence from 1 to N about
the circumference of the anode 42.
FIG. 4b represents a particular embodiment of the anode 42 designed
to encourage pi-mode oscillation at the desired operating
frequency. The aforementioned slots 80 are actually comprised of
long slots 80a and short slots 80b. The long slots 80a and short
slots 80b are arranged at intervals of .lambda./4 in alternating
fashion as shown in FIG. 4b. The long slots 80a and short slots 80b
have a depth ratio of 2:1 and an average depth of .lambda./4 in the
preferred embodiment. Consequently, the long slots 80a have a depth
dI equal to .lambda./3 and the short slots 80b have a depth ds
equal to .lambda./6. Such arrangement of long and short slots is
known in the microwave bands as a "rising sun" configuration. Such
configuration promotes pi-mode oscillation with the long slots 80a
lagging in phase and the short slots 80b leading in phase.
Although not shown in FIGS. 4a and 4b, one or more of the resonant
cavities formed by the respective slots 80 will include one or more
coupling ports 64 which couple energy from within the common
resonant cavity 66 as represented in FIGS. 2 and 3, for example,
into the respective slots 80 and the anode-cathode space 44
therein. Alternatively, the coupling port(s) 64 serve to couple
energy from the input window 76 directly into one or more of the
respective slots 80 and the anode-cathode space 44 therein, as
discussed below in connection with the embodiment of FIGS. 9 and
10, for example. The coupling ports 64 preferably are provided with
respect to slots 80 which are in phase with each other so as to add
constructively. Alternatively, one or more phase shifters may be
used to adjust the phase of radiation from the coupling ports 64 so
as to all be in phase.
FIG. 4c represents another particular embodiment of the anode 42
designed to encourage pi-mode oscillation at the desired operating
frequency. Such embodiment of the anode 42 is specifically
represented in the embodiment of FIGS. 2 and 3. An external
stabilizing resonator in the form of the common resonant cavity 66
serves to encourage pi-mode oscillation in accordance with the
invention. Specifically, every other slot 80 (i.e., either every
even-numbered slot or every odd-numbered slot) is coupled to the
resonant cavity 66 via a respective coupling port 64 so as to all
be in phase. The slots 80 are spaced at intervals of .lambda./2 and
otherwise each has a depth d equal to .lambda./4.
As will be appreciated, the slots 80 in each of the embodiments
described herein represent micro resonators. The following table
provides exemplary dimensions, etc. for an optical magnetron
generator 22 in accordance with the present invention. In the case
of a practical sized device in which the collector 40 has a radius
rc of 2 millimeters (mm) and the anode 42 has an inner radius ra of
7 mm, a length of 1 centimeter (cm), a magnetic field B of 2
kilogauss, and an electric field E potential of 30 kV to 50 kV, the
dimensions relating to the slots 80 in the case of the
configuration of FIG. 4c may be as follows, for example:
TABLE Operating Wavelength Slot Width w Slot Depth d .lambda. (mm)
Number of Slots N (microns) (microns) 10.sup.-2 87,964 1.25 2.5 3.5
.times. 10.sup.-3 251,324 0.4375 0.875 1.5 .times. 10.sup.-3
586,424 0.1875 0.375 0.5 .times. 10.sup.-3 1,759,274 0.0625
0.125
The output power for such an optical magnetron generator 22 will be
on the order of 1 kilowatt (kW) continuous. In addition,
efficiencies will be on the order of 85%. Consequently, the
generator 22 of the present invention is well suited for any
application which utilizes a high efficiency, high power conversion
of optical radiation to electrical power.
The micro resonators or resonant cavities formed by the slots 80
can be manufactured using a variety of different techniques
available from the semiconductor manufacturing industry. For
example, existing micromachining techniques are suitable for
forming slots having a width of 2.5 microns or so. Although
specific manufacturing techniques are described below, it will be
generally appreciated that an electrically conductive hollow
cylinder anode body may be controllably etched via a laser beam to
produce slots 80 having the desired width and depth. Alternatively,
photolithographic techniques may be used in which the anode 42 is
formed by a succession of electrically conductive layers stacked
upon one another with teeth representing the slots 80. For higher
frequency applications (e.g., .lambda.=0.5.times.10.sup.-4 mm),
electron beam (e-beam) techniques used in semiconductor processing
may be used to form the slots 80 within the anode 42. In its
broadest sense, however, the present invention is not limited to
any particular method of manufacture.
Referring now to FIG. 5, another embodiment of the optical
magnetron generator in accordance with the present invention is
generally designated 22a. The cathode 51 is not shown in FIG. 5 so
as to facilitate viewing. Such embodiment is virtually identical to
the embodiment of FIGS. 2 and 3 with the following exception. The
common resonant cavity 66 in this embodiment has a curved outer
wall 70 so as to form a toroidal shaped resonant cavity 66. The
radius of curvature of the outer wall 70 is on the order of 2.0 cm
to 2.0 m, depending on the operating frequency. The toroidal shaped
resonant cavity 66 serves to improve the ability of the common
resonant cavity 66 to control the pi-mode oscillations at the
desired operating frequency.
It is noted that each of the coupling ports 64 from the even
numbered slots 80, for example, are aligned horizontally at the
center of the anode 42 with the vertex of the curved outer wall 70.
This tends to focus the resonant optical radiation towards the
center of the anode 42 and reduce light leakage from the ends of
the cylindrical anode 42. The odd numbered slots 80 do not include
such coupling ports 64 and consequently are driven to oscillate out
of phase with the even numbered slots 80.
FIG. 6 illustrates another embodiment of the optical magnetron
generator which is generally designated 22b. Again, the cathode 51
has been omitted from the figure to facilitate viewing. The
embodiment of FIG. 6 is virtually identical to that of FIG. 5 with
the following exceptions. In this particular embodiment, the
magnetron generator 22b comprises a double toroidal common
resonator. More specifically, the magnetron generator 22b includes
a first toroidal shaped resonant cavity 66a and a second toroidal
shaped resonant cavity 66b formed in the resonant cavity structure
72. Each of the even-numbered slots 80 among the N total slots 80
is coupled by a coupling port 64a to the first cavity 66a. Each of
the odd-numbered slots 80 among the N total slots 80 is coupled to
the second cavity 66b by way of a coupling port 64b.
The first resonant cavity 66a is a higher frequency resonator
designed to lock a resonant mode at a frequency which is slightly
higher than the desired operating frequency. The second resonant
cavity 66b is a lower frequency resonator designed to lock a
resonant mode at a frequency which is slightly lower than the
desired frequency, such that the entire device oscillates at an
intermediate average frequency corresponding to the desired
operating frequency. The higher frequency modes within the first
resonant cavity 66a will tend to lead in phase while the low
frequency modes in the second resonant cavity 66b lag in phase
about the desired operation frequency. Consequently, pi-mode
operation will result.
Input radiation 24 may be provided from one or both of the input
port(s) 74a and 74b. As in the previous embodiment, the radii of
curvature for the outer walls 70a and 70b of the cavities 66a and
66b, respectively, are on the order of 2.0 cm to 2.0 m. However,
the radii of curvature are designed slightly shorter and longer for
the walls 70a and 70b, respectively, in order to provide the
desired high/low frequency operation with respect to the desired
operating frequency.
In a different embodiment, more than two resonant cavities 66 may
be formed around the anode 42 for constraining operation to the
pi-mode. The present invention is not necessarily limited to a
particular number. Furthermore, the cavities 66a and 66b in the
embodiment of FIG. 6 may instead be designed to both operate at the
desired operating frequency rather than offset as previously
described and as will be appreciated.
Turning now to FIGS. 7a and 7b, still another embodiment of an
optical magnetron generator is shown, this time designated as 22c.
As with all of the remaining embodiments, the cathode 51 is omitted
for better viewing. This embodiment illustrates how every other
slot 80 (i.e., all the even numbered slots or all the odd numbered
slots) may include more than one coupling port 64 to couple energy
between the respective resonant cavity and the common resonant
cavity 66. For example, FIG. 7a illustrates how even numbered slots
80 formed in the anode 42 alternate having three and four coupling
ports 64 in the respective slots 80. As in the other embodiments,
the coupling ports 64 couple energy to/from the common resonant
cavity 66 in order to better control the oscillation modes and
induce pi-mode operation. As is also shown in FIGS. 7a and 7b, the
optical magnetron generator 22c may include multiple input ports
74a, 74b, 74c, etc. for coupling the coherent optical input
radiation 24 from the input window 76 into the resonant cavity 66.
By forming an array of input ports 74 and/or coupling ports 64 as
described herein, it is possible to control the amount of coupling
which occurs as will be appreciated.
Although not shown in FIG. 7a, it will be appreciated that the
common resonant cavity 66 could be replaced with a toroidal shaped
cavity as in the embodiment of FIG. 5, for example. Moreover, it
will be readily appreciated that an optical magnetron generator 22
in accordance with the invention may be constructed by any
combination of the various features and embodiments described
herein, namely (i) an anode structure comprising a plurality of
small resonant cavities 80 which may be scaled according to the
desired operating wavelength to sizes as small as optical
wavelengths; (ii) a structure for constraining the resonant
cavities 80 to operate in the so-called pi-mode whereby each
resonant cavity 80 is constrained to oscillate pi-radians out of
phase with its nearest neighbors; and (iii) means for coupling the
optical input radiation 24 to the resonant cavities to induce
conversion to electrical output power. Different slot 80
configurations are discussed herein, as are different forms of one
or more common resonant cavities for constraining the resonant
cavities. In addition, the description herein provides means for
coupling power from the resonant cavities via the various forms and
arrangements of coupling ports 64 and input ports 74. On the other
hand, the present invention is not intended to be limited in its
broadest sense to the particular configurations described
herein.
Referring briefly to FIG. 8, a vertically stacked multifrequency
embodiment of the present invention is shown. In this embodiment,
the anode 42 is divided into an upper anode 42a and a lower anode
42b. In the upper anode 42a, the slots 80a are designed with a
width, spacing and number corresponding to a first operating
wavelength .lambda..sub.1. The slots 80b in the lower anode 42b, on
the other hand, are designed with a width, spacing and number
corresponding to a second operating wavelength .lambda..sub.2
different from the first operating wavelength .lambda..sub.1.
Even-numbered slots 80a, for example, in the upper anode 42a
include coupling ports 64a which couple energy between a rotating
electron cloud formed in the upper anode 42a and an upper common
resonant cavity 66a. Likewise, even-numbered (or odd numbered)
slots 80b in the lower anode 42b include coupling ports 64b which
couple energy between a rotating electron cloud formed in the lower
anode 42b and a lower common resonant cavity 66b. The upper and
lower common resonant cavities 66a and 66b serve to promote pi-mode
oscillation at the respective frequencies at wavelengths
.lambda..sub.1 and .lambda..sub.2 in the upper and lower anodes 42a
and 42b. Coherent optical input radiation 24 at the respective
frequencies having wavelengths .lambda..sub.1 and .lambda..sub.2 is
input respectively into the common resonant cavities 66a and 66b
through the input window 76 via one or more input ports 74a and
74b, respectively.
Thus, the present invention as represented in FIG. 8 provides a
manner for vertically stacking two or more anode resonators each
having a different operating wavelength (e.g., .lambda..sub.1 and
.lambda..sub.2). The anodes (e.g., upper and lower anodes 42a and
42b) may be stacked vertically between a single pair of magnets 58
and 60. The stacked device may therefore convert multiple
frequencies into electrical power.
FIGS. 9 and 10 illustrate an embodiment of the invention which
provides direct coupling of the input radiation 24 into the
anode-collector space 44 via the input window 76 and the coupling
ports 64. FIG. 10 illustrates how the rotating electron cloud
within the anode-collector space 44 creates fringing fields 90 at
the opening of the slots 80 and the coupling ports 64 therein as
the cloud passes by. The fringing fields 90 at the openings of the
coupling ports are emitted from the opposite side of the anode 42
as radiation fields 92. In turn, the radiation fields 92 interact
constructively with the input radiation 24 introduced via the input
window 76 so as to result in pi-mode bunching.
In the other embodiments described herein, the input radiation 24
is first introduced into a common resonant cavity 66. The common
resonant cavity 66 provides improved control of the pi-mode
operation as previously discussed. Nevertheless, the present
invention contemplates an embodiment which is perhaps less
efficient but also useful in which the coupling ports 64 couple the
input radiation 24 from the input window 76 directly into the
anode-collector space 44. In such case, as is shown in FIG. 9,
there is no need for coupling ports 64 in the slots 80 other than
those which couple the input radiation 24 from the input window 76.
The coupling principles of FIG. 10, however, apply to all of the
coupling ports 64 and input ports 74 discussed herein as will be
appreciated.
FIGS. 11a-11c illustrate an embodiment of an optical magnetron
generator 22e designed for operation in the TEM.sub.20 mode in
accordance with the present invention. The embodiment is similar to
that described above in connection with FIG. 5 in that it includes
a toroidal shaped resonant cavity 66 with a curved outer wall 70.
The embodiment differs from that of FIG. 5 in that even numbered
slots 80 have a single coupling port 64a which is aligned with
vertex of the curved outer wall 70 as is shown in FIG. 11b.
Consequently, the even numbered slots 80 tend to excite the central
spot 100 of the resonant cavity 66.
On the other hand, the odd numbered slots 80 include two coupling
ports 64b and 64c offset vertically on opposite sides of the vertex
of the curved outer wall 70 as is shown in FIG. 11c. Consequently,
the odd numbered slots 80 will tend to excite outer spots 102 of
the resonant cavity 66. The result is a TEM.sub.20 single mode
within the toroidal shaped resonant cavity 66. The central spot 100
has an electric field direction (e.g., out of the page in FIGS. 11b
and 11c) which is opposite the electric field direction (e.g., into
the page) of the outer spots 102. The electric fields change
direction each half-cycle of the oscillation. The even-numbered
slots 80 will thus have their electric fields driven out-of-phase
with respect to the odd-numbered slots 80, and the slots 80 are
forced to operate in the desired pi-mode.
FIGS. 11d-11f represent an embodiment of an optical magnetron
generator 22f which, in this case, is designed for operation in the
TEM.sub.10 mode according to the present invention. Again, the
embodiment is similar to that described above in connection with
FIG. 5 in that it includes a toroidal shaped resonant cavity 66
with a curved outer wall 70. This embodiment differs from that of
FIG. 5 in that even numbered slots 80 have a coupling port 64a
which is offset above the vertex of the curved outer wall 70 as
shown in FIG. 11e. As a result, the even numbered slots 80 tend to
excite an upper spot 104 of the resonant cavity 66.
The odd numbered slots 80, conversely, include a coupling port 64b
which is offset below the vertex of the curved outer wall 70 as is
shown in FIG. 11f. As a result, the odd numbered slots 80 tend to
excite a lower spot 106 of the resonant cavity 66. In this case,
the result is a TEM.sub.10 single mode within the toroidal shaped
resonant cavity 66. The upper spot 104 has an electric field
direction (e.g., into the page in FIGS. 11e and 11f) which is
opposite the electric field direction (e.g., out of the page) of
the lower spot 106. A small protrusion 108, or "spoiler" may be
provided around the circumference of the resonant cavity 66 at the
vertex of the curved outer wall 70 to help suppress the TEM.sub.00
mode. The respective electric fields of the upper and lower spots
change direction each half-cycle of the oscillation. The even
numbered slots 80 thus have their electric fields driven
out-of-phase with respect to the odd numbered slots 80, and the
slots 80 are forced to operate in the desired pi-mode.
FIGS. 11a-11f present two possible single modes in accordance with
the present invention. It will be appreciated, however, that other
TEM modes may also be used for pi-mode control without departing
from the scope of the invention.
As far as manufacture, the collector 40 of the magnetron generator
22 may be formed of any of a variety of electrically conductive
metals as will be appreciated. The collector 40 may be solid or
simply plated with an electrically conductive metal such as copper,
gold or silver, or may be fabricated from a spiral wound thoriated
tungsten filament, for example.
The anode 42 is made of an electrically conductive metal and/or of
a non-conductive material plated with a conductive layer such as
copper, gold or silver. The resonant cavity structure 72 may or may
not be electrically conductive, with the exception of the walls of
the resonant cavity or cavities 66 and output ports 74 which are
either plated or formed with an electrically conductive material
such as copper, gold or silver. The anode 42 and resonant cavity
structure 72 may be formed separately or as a single integral piece
as will be appreciated.
FIGS. 12a and 12b illustrate an exemplary manner for producing an
anode 42 using an electron beam lithography approach. A cylindrical
hollow aluminum rod 110 is selected having a radius equal to the
desired inner radius r.sub.a of the anode 42. A layer 112 of
positive photoresist, for example, is formed about the
circumference of the rod 110 as is shown in FIG. 12a. The length I
of the resist layer 112 along the axis of the rod 110 should be
made on the order of the desired length of the anode 42 (e.g., 1
centimeter (cm) to 2 cm). The thickness of the of the resist layer
112 is controlled so as to equal the desired depth of the resonant
cavities or slots 80.
The rod 110 is then placed in a jig 114 within an electron beam
patterning apparatus used for manufacturing semiconductors, for
example, as is represented in FIG. 12b. An electron beam 116 is
then controlled so as to pattern by exposure individual lines along
the length of the of the resist layer 112 parallel with the axis of
the rod 110. As will be appreciated, these lines will serve to form
the sides of the resonant cavities or slots 80 in the anode 42. The
lines are controlled so as to have a width equal to the spacing
between adjacent slots 80 (e.g., the quantity .lambda./2-.lambda./8
in the case of the embodiments such as FIG. 4a and FIG. 4c). The
lines are spaced apart from each other by the desired width w of
the slots 80 (e.g., .lambda./8 in the case of embodiments such as
FIG. 4a and FIG. 4c). The patterned resist layer 112 is then
developed and etched such that the exposed portion of the resist
layer 112 is removed. This results in the rod 110 having several
small fins or vanes, formed from resist, respectively corresponding
to the slots 80 which are to be formed in the anode 42. The rod 110
and the corresponding fins or vanes are then copper electroplated
to a thickness corresponding to the desired outer diameter of the
anode 42 (e.g., 2 mm). As will be appreciated, the copper plating
will form around the fins or vanes until the plating ultimately
covers the rod 110 substantially uniformly.
The aluminum rod 110 and fins or vanes made of resist are then
removed from the copper plating by chemically dissolving the
aluminum and resist with any available solvent known to be
selective between aluminum/resist and copper. Similar to the
technique known as lost wax casting, the remaining copper plating
forms an anode 42 with the desired resonant cavities or slots
80.
It will be appreciated that the equivalent structure may be formed
via the same techniques except with a negative photoresist and
forming an inverse pattern for the slots, etc.
Slots 80 having different depths, such as in the embodiment of FIG.
4b, may be formed using the same technique but with multiple layers
of resist. A first layer of resist 112 is patterned and etched to
form the fins or vanes on the aluminum rod 110 corresponding to
both the long slots 80a and the short slots 80b (FIG. 4b). The
first layer of resist 112 has a thickness ds corresponding to the
depth of the short slots. A second and subsequent layer of resist
112 is formed on the first patterned layer. The second layer 112 is
patterned to form the remaining portion of the fins or vanes which
will be used to form the long slots 80. In other words, the second
layer 112 has a thickness of dl-ds. The various coupling ports 64
may be formed in the same manner, that is with additional layers of
resist 112 in order to define the coupling ports 64 at the desired
locations. The rod 110 and resist is then copper plated, for
example, to form the anode 42 with the rod 110 and resist
subsequently being dissolved away. The same technique for forming
the coupling ports 64 may be applied to the above-described
manufacturing technique for the embodiment of FIG. 4c, as will be
appreciated.
FIG. 13 illustrates the manner in which the anode 42 may be formed
as a vertical stack of layers using known
micromachining/photolithography techniques. A first layer of metal
such as copper is formed on a substrate. A layer of photoresist is
then formed on the copper and thereafter the copper is patterned
and etched (e.g., via electron beam) so as to define the resonant
cavities or slots 80 in a plane normal to the axis of the anode 42.
Subsequent layers of copper are then formed and etched atop the
original layers in order to create a stack which is subsequently
the desired length of the anode 42. As will be appreciated,
planarization layers of oxide or some other material may be formed
in between copper layers and subsequently removed in order to avoid
filling an existing slot 80 when depositing a subsequent layer of
copper, for example. Also, such oxide may be used to define
coupling ports 64 as desired, such oxide subsequently being removed
by a selective oxide/copper etch.
As will be appreciated, known photolithography and micromachining
techniques used in the production of semiconductor devices may be
used to obtain the desired resolution for the anode 42 and
corresponding resonant cavities (e.g., slots 80). The present
invention nevertheless is not intended to be limited, in its
broadest sense, to the particular methods described herein.
FIGS. 14a-14c illustrate a technique for forming the resonant
cavity structure 72 with a toroidal shape as described herein. For
example, an aluminum rod 120 is machined so as to have bump 122 in
the middle as shown in FIG. 14a. The radius of the rod 120 in upper
and lower portions 124 is set equal to approximately the outer
radius of the anode 42 around which the structure 72 will fit. The
bump 122 is machined so as to have a radius corresponding to the
vertex point of the structure 72 to be formed.
Thereafter, the bump 122 is rounded to define the curved toroidal
shape of the wall 70 as described above. Next, the thus machined
rod 112 is electroplated with copper to form the structure 72
therearound as represented in FIG. 14b. The aluminum rod 120 is
then chemically dissolved away from the copper structure 72 so as
to result in the structure 72 as shown in FIG. 14c. Output ports 74
may be formed as needed using micromachining (e.g., via laser
milling), for example.
Reference is now made to FIGS. 15-38 which relate to a variety of
different anode structures 42 suitable for use in alternative
embodiments of an optical magnetron generator in accordance with
the present invention. As will be appreciated, the anodes 42 as
shown in FIGS. 15-38 can be substituted for the anode 42 in the
other embodiments previously discussed herein, for example the
embodiments of FIGS. 5-9. Again, each of the anodes 42 has a
generally hollow-cylindrical shape with an inner surface 50
defining the anode-collector space 44 into which the cathode 51 and
collector 40 (not shown) are coaxially placed. Depending on the
particular embodiment, one or more common resonant cavities 66 (not
shown) are formed around the outer circumference of the anode 42
via a resonant cavity structure 72 (also not shown) as in the
previous embodiments. Since only the structure of the anode 42
itself differs in relevant part with respect to the various
embodiments discussed herein, the following discussion is limited
to the anode 42 for sake of brevity. It will be appreciated by
those skilled in the art that the present invention contemplates an
optical magnetron generator as previously discussed herein
incorporating any and all of the different anode structures 42.
Moreover, it will be appreciated that the anode structures 42 may
have utility as part of a magnetron generator in bandwidths outside
of the optical range, and are considered part of the invention.
In particular, FIGS. 15-18 represent an anode 42 in accordance with
an alternate embodiment of the present invention. As is shown in
FIG. 15, the anode 42 has a hollow-cylindrical shape with an inner
surface 50 and an outer surface 68. Like the previous embodiments
discussed above, a plurality N (where N is an even number) of slots
or cavities 80 are formed along the inner surface 50. Again, the
slots 80 serve as resonant cavities. The number and dimensions of
the slots or cavities 80 depends on the desired operating
wavelength .lambda. as discussed above. The anode 42 is formed by a
plurality of pie-shaped wedge elements 150, referred to herein
simply as wedges. When stacked side by side, the wedges 150 form
the structure of the anode 42 as shown in FIG. 15.
FIG. 16 is a top view of an exemplary wedge 150. Each wedge 150 has
an angular width .phi. equal to (2.pi./N) radians, and an inner
radius of ra equal to the inner radius ra of the anode 42. The
outer radius ro of the wedge 150 corresponds to the outer radius ro
of the anode 42 (i.e., the radial distance to the outer surface 68.
Each wedge 150 further includes a recess 152 formed along the apex
of the wedge 150 which defines, in combination with the side wall
154 of an adjacent wedge 150, one of the N resonant cavities
80.
As is shown in FIG. 16, each recess 152 has a length equal to d,
which is equal to the depth of each resonant cavity 80. In
addition, each recess 152 has a width w which is equal to the width
of each resonant cavity 80. Thus, when stacked together
side-by-side, the wedges 150 form N resonant cavities 80 around the
inner surface 50 of the anode 42. The number N, depth, width and
spacing therebetween of resonant cavities 80 is selected based on
the desired operating wavelength as discussed above, and the
dimensions of the wedges 150 are selected accordingly. The length L
of each wedge 150 (see, e.g., FIG. 17), is set equal to the desired
height of the anode 42 as will be appreciated.
As in the embodiments discussed above, the wedges 150 may be
nominally considered as even and odd-numbered wedges 150 arranged
about the circumference of the anode 42. The even-numbered wedges
150 include a recess 152 to produce even-numbered cavities 80 and
the odd-numbered wedges 150 include a recess 152 which produces
odd-numbered cavities 80. FIGS. 17 and 18 show the front sides of
even and odd-numbered wedges 150a and 150b, respectively. The front
sides of the even-numbered and odd-numbered wedges 150a and 150b
include a recess 152 as shown in FIGS. 17 and 18, respectively. In
addition, however, each of the odd-numbered wedges 150b include a
coupling port recess 164 as shown in FIG. 18. Each coupling port
recess 164 in combination with the back side wall 154 of an
adjacent wedge 150a forms a coupling port 64 acting as a single
mode waveguide which serves to couple energy from the odd-numbered
cavities 80 to a common resonant cavity 72. It is noted that only
one of such coupling ports 64 is shown in FIG. 15 by way of
example. As will be appreciated, the back side wall 154 of each
wedge 150 is substantially planar as is the front side wall 166 of
each wedge 150. Thus, the recesses 152 and 164 combine with the
back side wall 154 of an adjacent wedge 150 to form a desired
resonant cavity 80 and coupling port 64.
The wedges 150 may be made from various types of electrically
conductive materials such as copper, aluminum, brass, etc., with
plating (e.g., gold) if desired. Alternatively, the wedges 150 may
be made of some non-conductive material which is plated with an
electrically conductive material at least in the regions in which
the resonant cavities 80 and coupling ports 64 are formed.
The wedges 150 may be formed using any of a variety of known
manufacturing or fabrication techniques. For example, the wedges
150 may be machined using a precision milling machine.
Alternatively, laser cutting and/or milling devices may be used to
form the wedges. As another alternative, lithographic techniques
may be used to form the desired wedges. The use of such wedges
allows precision control of the respective dimensions as
desired.
After the wedges 150 have been formed, they are arranged in proper
order (i.e., even-odd-even-odd . . . ) to form the anode 42. The
wedges 150 may be held in place by a corresponding jig, and the
wedges soldered, brazed or otherwise bonded together to form an
integral unit.
The embodiment of FIGS. 15-18 is analogous to the embodiment of
FIG. 5 in that only the even/odd numbered cavities 80 include a
coupling port 64, whereas the odd/even numbered cavities 80 do not
include such a coupling port 64. The coupling of every other cavity
80 to the common resonant cavity 66 serves to induce pi-mode
operation in the same manner.
FIGS. 19-23 relate to another embodiment of an anode 42. Such
embodiment is generally similar insofar as wedge-based
construction, and hence only the differences will be discussed
herein for sake of brevity. FIG. 19 illustrates the anode 42 in
schematic cross section. In this particular embodiment, each
resonant cavity 80 includes a coupling port or ports 64 each acting
as a single mode waveguide for coupling energy between the resonant
cavity 80 and one or more common resonant cavities 66 in order to
induce further pi-mode operation. The coupling ports 64 formed by
the odd-numbered wedges 150b introduce an additional 1/2.lambda.
delay in relation to the coupling ports 64 formed by the
even-numbered wedges 150a, so as to provide the appropriate phase
relationship.
FIG. 19 illustrates how the odd-numbered wedges 150b in this
particular embodiment include a recess 164b which extends radially
and at an angle in the H-plane direction between the recess 152
which forms the corresponding resonant cavity 80 and the outer
surface 68 of the anode 42. The even-numbered wedges 150a, on the
other hand, each include a pair of recesses 164a that each extend
radially and perpendicular to the center axis between the recess
152 which forms the corresponding resonant cavity 80 and the outer
surface 68. (It will be appreciated that the even-numbered wedge
150 as shown in FIG. 19 is flipped with respect to its intended
orientation in order to provide a clear view of the recesses
164a).
The angle at which the recesses 164b are formed in the odd numbered
wedges is selected so as each to introduce overall an additional
1/2.lambda. delay compared to the recesses 164a. Thus, radiation
which is coupled between the resonant cavities 80 formed by the
even and odd-numbered wedges 150 will have the appropriate phase
relationship with respect to the common resonant cavity 66.
FIGS. 22 and 23 illustrate how the odd-numbered wedges 150b in the
embodiment of FIG. 19 alternate between upwardly directed and
downwardly directed angles. This allows for a more even
distribution of the energy with respect to the axial direction
within the anode-cathode space and the common resonant cavity 66
(not shown), as will be appreciated.
FIGS. 24-27 illustrate another embodiment of the anode 42 using an
H-plane bend of the coupling ports 64 formed by the odd-numbered
wedges to introduce an additional 1/2.lambda. delay relative to the
coupling ports 64 formed by the even-numbered wedges. The
even-numbered wedges 150a are similar to those in the embodiment of
FIGS. 19-23. However, the odd-numbered wedges 150b include a pair
of recesses 164b each presented at an angle relative to the
H-plane. Each of the recesses 164b is designed to form a single
mode waveguide in combination with the back side wall 154 of an
adjacent wedge 150a. The recesses 164b are bent along the H-plane
so as each to provide an additional 1/2.lambda. delay compared to
the recesses 164a in the even-numbered wedges. Consequently, the
desired phase relationship between the resonant cavities 80 and one
or more surrounding common resonant cavities 66 (not shown) is
provided for pi-mode operation. Moreover, because each of the
recesses 164b include a pair of bends 170 and 172, the coupling
ports 64 formed by the recesses are generally evenly distributed
along the axial direction of the anode 42. Thus, such an embodiment
may be more favorable than the embodiment of FIGS. 19-23 which
called for two different odd-numbered wedges 150b1 and 150b2. It
will also be appreciated that again the even-numbered wedge 150a as
shown in FIG. 24 is flipped with respect to its intended
orientation in order to provide a clear view of the recesses
164a.
FIGS. 28 and 29 illustrate yet another embodiment of a wedge-based
construction of an anode 42. This embodiment differs from the
embodiment of FIGS. 19-23 in the following manner. The
even-numbered wedges 150a include three recesses 164a rather than
two. The odd-numbered wedges 150b1 and 150b2 include two recesses
164b rather than one. As will be appreciated, the number of
recesses 164 formed in the respective wedges 150 is not limited to
any particular number in accordance with the present invention. The
number of recesses 164 may be selected based on the desired amount
of coupling between the anode-cathode space and the common resonant
cavity or cavities 66, as will be appreciated. It will again be
appreciated that the even-numbered wedge 150a as shown in FIG. 28
is flipped with respect to its intended orientation in order to
provide a clear view of the recesses 164a.
Referring now to FIGS. 30-33, yet another embodiment of an anode 42
is presented which utilizes an additional 1/2.lambda. delay in the
coupling ports 64 formed by the even-numbered wedges 150a compared
to the odd-numbered wedges 150b to induce pi-mode operation. In
this embodiment, however, the additional 1/2.lambda. delay is
provided by adjusting the relative width of the recesses 164 (as
compared to introducing an H-plane bend). More particularly, each
odd-numbered wedge 150b includes a pair of recesses 164b which
combine with the back side wall 154 of an adjacent wedge 150a to
form single mode waveguides serving as coupling ports 64. The
even-numbered wedges 150a, on the other hand, include recesses 164a
which have a width 174 that is relatively wider than that of the
recesses 164b. As is known from waveguide theory, an appropriately
selected wider width 174 of the recesses 164a may be chosen to
provide for an additional 1/2.lambda. delay compared to that of the
recesses 164b. Thus, the desired phase relationship between the
coupling ports 64 formed by the odd-numbered and even-numbered
wedges may be obtained for pi-mode operation.
FIGS. 34-38 relate to an embodiment of the anode 42 which utilizes
bends in the E-plane of the coupling ports 64 to provide the
desired additional 1/2.lambda. delay for pi-mode operation. As is
shown in FIG. 34, the anode 42 is made up of several layers 180
stacked on top of each other with or without a spacer member (not
shown) therebetween. The layers 180 are nominally referred to as
either an even-numbered layer 180a or an odd-numbered layer 180b
which alternate within the stack. The even-numbered layers 180a
include linear waveguides forming coupling ports 64 which serve to
couple energy between the anode-collector space and one or more
common resonant cavities 66 (not shown). The odd-numbered layers
180b include waveguides which are curved in the E-plane and form
coupling ports 64 which also serve to couple energy between the
anode-collector space and the one or more common resonant cavities
66. The waveguides in the odd-numbered layers 180b are curved so as
to introduce an additional 1/2.lambda. delay compared to the
waveguides in the even-numbered layers 180a to provide the desired
pi-mode operation.
FIGS. 35 and 36 illustrate an exemplary even-numbered layer 180a.
Each layer 180a is made up of N/2 guide elements 182, where N is
the desired number of resonant cavities 80 as above. The guide
elements 182 are each formed in the shape of a wedge as shown in
FIG. 36. The guide elements 182 are arranged side by side as shown
in FIG. 35 to form a layer which defines the inner surface 50 and
outer surface 68 of the anode 42. The tip of each wedge includes a
slot which defines a resonant cavity 80 therein. In addition,
adjacent guide elements 182 are spaced apart so as to form a
resonant cavity 80 therebetween as shown in FIG. 36. As will be
appreciated, the resonant cavities 80 formed in each of the layers
180 are to be aligned when the layers 180 are stacked together.
Aligning holes or marks 184 may be provided in the elements 182 to
aid in such alignment between layers.
As best shown in FIG. 36, the space between the guide elements 182
defines a radial tapered waveguide which serves as a coupling port
64 between an even-numbered resonant cavity 80 and the outer
surface 68 of the anode 42. The thickness of the guide elements 182
is provided such that the coupling ports 64 have an H-plane height
corresponding to the desired operating wavelength .lambda..
Similarly, the dimensions of the resonant cavities 80 and the
spacing between the guide elements 182 are selected for the desired
wavelength .lambda..
The guide elements 182 are made of a conductive material such as
copper, polysilicon, etc. so as to define the conductive walls of
the resonant cavities and coupling ports 64. Alternatively, the
guide elements 182 may be made of a non-conductive material with
conductive plating at least at the portions defining the walls of
the resonant cavities and coupling ports 64.
A spacer element 186 (shown in part in FIG. 36) is formed between
adjacent layers 180 in the stack making up the anode 42. The spacer
186 is conductive at least in relevant part to provide the
conductive E-plane walls of the coupling ports 64 in the layers
180. The spacer 186 may be washer shaped with an inner radius equal
to the inner radius ra of the anode 42.
FIGS. 37 and 38 illustrate an exemplary odd-numbered layer 180b.
The odd-numbered layer 180b is similar in construction to that of
the even-numbered layer with the exception that the guide elements
182 are curved to provide a desired bend in the E-plane direction
of tapered waveguides forming the coupling ports 64. The particular
radius of curvature of the bend is calculated to provide the
desired additional 1/2.lambda. delay relative to the coupling ports
64 of the even-numbered layers 180a for pi-mode operation. Also,
the coupling ports 64 in the odd-numbered layers 180b serve to
couple the odd-numbered resonant cavities 80 to the outer surface
68 of the anode 42, rather than the even-numbered resonant cavities
80 as in the even-numbered layers 180a.
The embodiment of FIGS. 34-38 is particularly well suited to known
photolithographic fabrication methods as will be appreciated. A
large anode 42 may be built up from layers 180b of E-plane bends
interposed between layers 180a of straight waveguides. The layers
may be formed and built up using photolithographic techniques. The
appropriate dimensions for operation even at higher optical
wavelengths can be achieved with the desired resolution. The guide
elements 182 may be formed of copper or polysilicon, for example.
The waveguides forming the coupling ports 64 may be filled with a
suitable dielectric to provide planarization between layers 180 if
desired. The spacers 186 between layers 180 may be formed of
copper, polysilicon, etc., as will be appreciated.
In another embodiment, the layers 180 are generally identical with
coupling ports 64 leading from each of the resonant cavities 80
radially outward to the outer surface 68 of the anode. In this
case, however, the height of the coupling ports 64 corresponding to
the odd-numbered resonant cavities 80 is greater than the height of
the coupling ports 64 corresponding to the even-numbered resonant
cavities 80. The difference in height corresponds to a difference
in width as discussed above in relation to the embodiment of FIGS.
30-33, and is provided so as to produce the desired additional
1/2.lambda. delay relative to the coupling ports 64 of the
even-numbered resonant cavities 80 for pi-mode operation.
It will therefore be appreciated that the optical magnetron
generator of the present invention is suitable for converting
optical radiation to electrical power. The optical magnetron
generator of the present invention is capable of producing high
efficiency power conversion at frequencies within the microwave,
infrared and visible light bands, and which may extend beyond into
higher frequency bands such as ultraviolet, x-ray, etc. As a
result, the optical magnetron generator of the present invention
may serve as an electrical power source in a variety of
applications.
For example, power in the form of optical radiation may be beamed
to satellites or aircraft from ground stations. An on-board optical
magnetron generator serves to convert the optical radiation into
electric power which may be used as needed. Similarly, power from
orbiting power stations may be transmitted in the form of optical
radiation to an optical magnetron generator on earth. Such optical
radiation is converted into electrical power as an alternative to
environmentally damaging sources of energy.
Although the invention has been shown and described with respect to
certain preferred embodiments, it is obvious that equivalents and
modifications will occur to others skilled in the art upon the
reading and understanding of the specification. For example,
although slots are provided as the simplest form of resonant
cavity, other forms of resonant cavities may be used within the
anode without departing from the scope of the invention.
Furthermore, although the preferred techniques for providing
pi-mode operation have been described in detail, other techniques
are also within the scope of the invention. For example, cross
coupling may be provided between slots. The slots 80 are spaced by
1/2.lambda. and coupling channels are provided between adjacent
slots 80. The coupling channels from slot to slot measure
3/2.lambda.. In another embodiment, a plurality of optical
resonators are embedded around the circumference of the anode
structure with non-adjacent slots constrained to oscillate out of
phase by coupling to a single oscillating mode in a corresponding
one of the optical resonators. Other means will also be apparent
based on the description herein.
Additionally, it will be appreciated that the toroidal resonators
described herein which employ curved surfaces and TEM modes to
control pi-mode oscillation may be utilized in otherwise
conventional magnetrons.
The present invention includes all such equivalents and
modifications, and is limited only by the scope of the following
claims.
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